1. Field of the Invention
The present invention relates to axle/suspension systems, and in particular to lift assemblies or lift axle suspensions for axle/suspension systems of heavy-duty commercial vehicles. More specifically, the invention relates to a side-beam lift assembly that is located generally inboardly from and adjacent to the side of the hanger and the beam of the axle/suspension system, for lifting the axle/suspension system during operation of the vehicle.
2. Background Art
The use of air-ride trailing and leading arm rigid beam-type axle/suspension systems has been popular in the heavy-duty truck and tractor-trailer industry for many years. Air-ride trailing and leading arm spring beam-type axle/suspension systems also are often used in the industry. For the purpose of convenience and clarity, reference herein will be made to beams, with the understanding that such reference is by way of example, and that the present invention applies to heavy-duty vehicle air-ride axle/suspension systems that utilize rigid-type beams or spring-type beams. Although such axle/suspension systems can be found in widely varying structural forms, in general their structure is similar in that each system typically includes a pair of suspension assemblies. In some heavy-duty vehicles, the suspension assemblies are connected directly to the primary frame of the vehicle. In other heavy-duty vehicles, the primary frame of the vehicle supports a subframe, and the suspension assemblies connect directly to the subframe. For those heavy-duty vehicles that support a subframe, the subframe can be non-movable or movable, the latter being commonly referred to as a slider box, slider subframe, slider undercarriage, or secondary slider frame. For the purpose of convenience and clarity, reference herein will be made to main members, with the understanding that such reference is by way of example, and that the present invention applies to heavy-duty vehicle axle/suspension systems suspended from main members of: primary frames, movable subframes and non-movable subframes.
Specifically, each suspension assembly of an axle/suspension system includes a longitudinally extending elongated beam. Each beam typically is located adjacent to and below a respective one of a pair of spaced-apart longitudinally extending main members and one or more cross members which form the frame of the vehicle. More specifically, each beam is pivotally connected at one of its ends to a hanger, which in turn is attached to and depends from a respective one of the main members of the vehicle. The beams of the axle/suspension system can either be an overslung/top-mount configuration or an underslung/bottom-mount configuration. For the purposes of convenience and clarity hereinafter, a beam having an overslung/top-mount configuration shall be referred to as an overslung beam and a beam having an underslung/bottom-mount configuration shall be referred to as an underslung beam with the understanding that such reference is by way of example, and that the present invention applies to both overslung/top-mount configurations and underslung/bottom-mount configurations. An axle extends transversely between and typically is connected by some means to the beams of the pair of suspension assemblies at a selected location from about the mid-point of each beam to the end of the beam opposite from its pivotal connection end. The end of each beam opposite its pivotal connection end also is connected to a bellows air spring or its equivalent, which in turn is connected to a respective one of the main members. A height control valve is mounted on the hanger and is operatively connected to the beam in order to maintain the ride height of the vehicle. The beam may extend rearwardly or frontwardly from the pivotal connection relative to the front of the vehicle, thus defining what are typically referred to as trailing arm or leading arm axle/suspension systems, respectively. However, for purposes of the description contained herein, it is understood that the term “trailing arm” will encompass beams which extend either rearwardly or frontwardly with respect to the front end of the vehicle. One or more shock absorbers and a brake assembly also are mounted on the axle/suspension system.
Many commercial vehicles currently utilize suspension assemblies that can retract and thereby raise the axle of the axle/suspension system off the ground. Such suspension assemblies conventionally are known in the industry as lift axle suspensions or lift assemblies. Lift axle/suspension systems usually are paired or grouped with non-lift axle/suspension systems on a vehicle, the latter of which are commonly referred to as primary axle/suspension systems. The majority of lift axle/suspension systems utilize one or more pneumatic air springs to raise or retract the axle/suspension system. Pneumatic air springs of that type typically are referred to as air chambers and generally have been placed in a variety of locations relative to the axle/suspension system to accomplish the lifting function. Another set, usually a pair, of pneumatic air springs is utilized to lower or extend the axle/suspension system for assisting in supporting the vehicle load, and typically are referred to as ride air springs.
Lift axle/suspension systems usually are retracted or raised when the vehicle load is less than the load capacity of the primary or non-lift axle/suspension systems, or when greater vehicle maneuverability is required. A number of different types of pneumatic or electro-pneumatic systems have been employed to operate lift axle/suspension systems, depending on the application and end-user requirements. The present invention can be utilized with most types of such operating systems. Most such systems operate by simultaneously but independently supplying pressurized or compressed air to the air chambers of the lift assembly and exhausting air pressure from the ride air springs when it is desired to retract or raise the lift axle/suspension system. Conversely, when it is desired to lower the lift axle/suspension system to support a load, air pressure is supplied to the ride air springs and exhausted from the lift air springs.
Although many known prior art lift axle suspensions or lift assemblies accomplish their goal of raising and lowering the axle/suspension system, certain drawbacks are inherent in those lift axle suspensions. More particularly, one example of prior art lift axle suspensions includes air chambers that are located generally beneath the hanger and the beam of the axle/suspension system. More specifically, the air chambers of the prior art lift axle suspension are mounted on the front portion of the hanger and extend below the hanger. The prior art lift axle suspension is also connected to the underside of the beam of the axle/suspension system by a pivot arm bracket that urges the beam upwardly when the lift air springs are inflated. These prior art lift axle/suspension systems are effective for applications where ground clearance is not an issue. However, in applications where ground clearance is minimized, such as in an application for a low-boy trailer having an underslung beam configuration, use of these prior art lift axle/suspension systems generally result in an inadequate amount of ground clearance, in turn resulting in impact of the components of the lift axle suspension with the ground, which can result in damage or reduced life of the lift axle suspension and/or the axle/suspension system.
Another example of known prior art lift axle suspensions includes a single air chamber that is located between the suspension assemblies of the axle/suspension system. Although this arrangement allows for increased ground clearance, it reduces the usable space between the suspension assemblies for trailer components such as air tanks, and drop center cross members. Moreover, because these prior art lift axle suspensions must span the entire width between the suspension assemblies, they are heavy and therefore reduce the amount of cargo that can be carried by the heavy-duty vehicle. In addition, they require lift assemblies having different widths to accommodate trailers having larger or smaller widths, thereby complicating assembly of the lift axle suspension.
Still other prior art lift axle suspensions include air chambers that are located generally in front of the hangers of the axle/suspension system. These prior art lift axle suspensions can affect the longitudinal spacing of the axle/suspension systems, thereby limiting the range of longitudinal axle spacing that is available between the axle/suspension systems.
There are many variations of the above-described prior art lift axle suspensions which exhibit the same disadvantages as those set forth above.
The preferred embodiment side-beam lift assembly of the present invention overcomes the problems associated with the prior art lift axle suspensions described above. More specifically, the preferred embodiment side-beam lift assembly of the present invention overcomes the problem of inadequate ground clearance found in some prior art lift axle suspensions by locating the air chamber of the lift assembly as well as the lift mechanism itself directly inboardly from and adjacent to the hanger and the beam, thereby providing increased ground clearance over the prior art lift assemblies. In addition, the side-beam lift assembly of the present invention has a reduced weight and provides additional useable space, particularly between the spaced-apart suspension assemblies of its axle/suspension system, for trailer components such as air tanks and drop-center cross members and the like. Moreover, the side-beam lift assembly of the present invention, because it includes a curb-side axle lift assembly for the curb-side suspension assembly and a driver-side axle lift assembly for the driver-side suspension assembly, is capable of being utilized on trailers having different widths without requiring any modification to the components of the lift assembly, thereby simplifying assembly of the lift axle suspension. Furthermore, because the side-beam lift assembly of the present invention is located entirely between the suspension beams of the axle/suspension system, it does not affect the longitudinal spacing of the axle/suspension systems, in turn allowing a wider range of available longitudinal axle spacing between the axle/suspension systems.